Boolean operators are tools that can help you find more relevant documents when searching a database with keywords. Boolean operators define relationships between two or more keywords to broaden or narrow your search.
The most common Boolean operators are terms like AND, OR, and NOT. Each of these can impact your search in different ways. The diagrams below show the impact of Boolean operators on a database search for articles using the keywords “cats” and “dogs.”
Search 1: cats AND dogs
AND narrows a search to only show results that include BOTH of your keywords. In the first diagram, the dark blue area represents that search, which only retrieved articles that include both cats and dogs.
Search 2:
cats OR dogs
OR expands a search to show results that include one, the other or both of your search terms. In the second and third diagrams, the light blue and dark green areas represent that search, which has retrieved articles that just include cats, just include dogs, and those that include both cats and dogs.
Search 3:
cats NOT dogs
NOT narrows a search to only show results that have one keyword, but not the other. In the last diagram, the dark purple area represents that search, which has only retrieved articles that include cats, not those that include dogs. It also excludes results that include both cats and dogs.
For tips about using Boolean operators, watch our video tutorial below, or visit the Research Tools page/ on the College Writing II LibGuide/.